Wound complications after median sternotomy: A study of 61 patients from a consecutive series of 9,279

Among a consecutive series of 9,279 sternotomies performed during a period of 2(1/2) years, 61 (0.66%) patients developed significant wound complications. Of these, 58 (95.1%) survived. Sternal infection occurred in 36 patients (0.39%). Predisposing factors included chronic obstructive pulmonary disease, diabetes mellitus, obesity, closed chest massage, prolonged assisted ventilation, and excessive bleeding after operation. Positive end expiratory pressure (PEEP) did not, in itself, predispose to sternal dehiscence. Intermittent positive pressure breathing (IPPB) treatments caused excessive coughing, which may have increased the likelihood of dehiscence. Disposable drapes and expeditious surgery probably contributed to the low incidence of wound infection. Early diagnosis, surgical debridement, rewiring and primary closure with substernal drainage, without continuous antibiotic irrigation, resulted in satisfactory resolution in most patients.     

Investigation of the pH dependence of proton uptake by porcine heart mitochondrial malate dehydrogenase upon binding of NADH

The pH dependence of proton uptake upon binding of NADH to porcine heart mitochondrial malate dehydrogenase (l-malate: NAD⁺ oxidoreductase, EC 1.1.1.37) has been investigated. The enzyme has been shown to exhibit a pH-dependent uptake of protons upon binding NADH at pH values from 6.0 to 8.5. Enzyme in which one histidine residue has been modified per subunit by the reagent iodoacetamide (E. M. Gregory, M. S. Rohrbach, and J. H. Harrison, 1971, Biochim. Biophys. Acta253, 489–497) was used to establish that this specific histidine residue was responsible for the uptake of a proton upon binding of NADH to the native enzyme. It has also been established that while there is no enhancement of the nucleotide fluorescence upon addition of NADH to the iodoacetamide-modified enzyme, NADH is nevertheless binding to the modified enzyme with the same stoichiometry as with native enzyme. The data are discussed in relation to the involvement of the essential histidine residue in the catalytic mechanism of “histidine dehydrogenases” recently proposed by Lodola et al. (A. Lodola, D. M. Parker, R. Jeck, and J. J. Holbrook, 1978, Biochem. J.173, 597–605) and the catalytic mechanism of “malate dehydrogenases” recently proposed by L. H. Bernstein and J. Everse (1978, J. Biol. Chem.253, 8702–8707).     

Separation of haemopoietic cells for biochemical investigation. Preparation of erythroid and myeloid cells from human and laboratory-animal bone marrow and the separation of erythroblasts according to their state of maturation.

The separation of haemopoietic bone-marrow cells by centrifugation through discontinuous density gradients of Percoll is described. This method was used to prepare fractions enriched in erythroblasts, myeloid blast cells or reticulocytes from bone marrow of anaemic and non-anaemic rabbits, from the marrow of other anaemic laboratory animals and from human samples. It is a simple, rapid, reproducible and inexpensive technique that can be readily adapted to suit individual requirements. Secondly, a convenient method is presented for the separation of large quantities of bone-marrow cells into fractions enriched in erythroblasts at different stages of maturation, by velocity sedimentation through a linear gradient of 1-2% sucrose at unit gravity. In vitro, erythroblasts adhere together strongly via a mechanism almost certainly involving a beta-galactoside-specific surface lectin termed erythroid developmental agglutinin. Since the efficiency of cell-separation techniques depends heavily on the maintenance of a single cell suspension in which each unit can move independently, the presence of an adhesive molecule at the cell surface is of considerable significance. The effect of washing the marrow with a lactose-containing medium, which has been shown to remove the agglutinin, was therefore investigated in relation to both methods. The separation on Percoll gradients is considerably enhanced by this treatment. In addition, the unit-gravity sedimentation gradient can be loaded with 5-10 times more cells after lactose extraction in comparison with intact marrow. Although enrichment is less, a useful fractionation according to maturation is still obtained.     

Dehydrogenation by gluconate 6-phosphate dehydrogenase of an isosteric phosphonate substrate analogue.

6,7-Dideoxy-D-gluco-heptonic-7-phosphonic acid, the isosteric phosphonate analogue of gluconate 6-phosphate, was prepared by incubation of the corresponding analogue of glucose 6-phosphate with glucose 6-phosphate dehydrogenase and NADP+ in the presence of an enzyme NADPH-NADP+ recycling system. The analogue of gluconate 6-phosphate is a substrate for yeast gluconate 6-phosphate dehydrogenase, showing Michaelis-Menten kinetics at pH 7.5 and 8.0. At both pH values the Km values are approx. 3-fold higher and the Vmax. values approx. 7-fold lower than those of the natural substrate.     

Pseudomycins, a family of novel peptides from Pseudomonas syringae possessing broad-spectrum antifungal activity.

A family of peptide antimycotics, termed pseudomycins, has been isolated from liquid cultures of Pseudomonas syringae, a plant-associated bacterium. These compounds were purified using Amberlite XAD-2 and reverse-phase liquid chromatography. Pseudomycin A, the predominant peptide in a family of four, showed selective phytotoxicity, and had impressive activity against the human pathogen Candida albicans. Amino acid, mass spectroscopic, and comparative electrophoretic and chromatographic analyses revealed that the pseudomycins are different from previously described antimycotics from P. syringae, including syringomycin, syringotoxin and syringostatins. Pseudomycins A-C contain hydroxyaspartic acid, aspartic acid, serine, arginine, lysine and diaminobutyric acid. The molecular masses of pseudomycins A-C, as determined by plasma desorption mass spectrometry, are 1224, 1208 and 1252 Da, respectively. Pseudomycin D, on the other hand, has a molecular mass of 2401 Da and is more complex than pseudomycins A-C.     

Influence of site-directed modifications on the formation of iron cores in ferritin

The structure and crystal chemical properties of iron cores of reconstituted recombinant human ferritins and their site-directed variants have been studied by transmission electron microscopy and electron diffraction. The kinetics of Fe uptake have been compared spectrophotometrically. Recombinant L and H-chain ferritins, and recombinant H-chain variants incorporating modifications in the threefold (Asp131----His or Glu134----Ala) and fourfold (Leu169----Arg) channels, at the partially buried ferroxidase sites (Glu62,His65----Lys,Gly), a putative nucleation site on the inner surface (Glu61,Glu64,Glu67----Ala), and both the ferroxidase and nucleation sites (Glu62,His65----Lys,Gly and Glu61,Glu64,Glu67----Ala), were investigated. An additional H-chain variant, incorporating substitution of the last ten C-terminal residues for those of the L-chain protein, was also studied. Most of the proteins assimilated iron to give discrete electron-dense cores of the Fe(III) hydrated oxide, ferrihydrite (Fe2O3.nH2O). No differences were observed for variants modified in the three- or fourfold channels compared with the unmodified H-chain ferritin. The recombinant L-chain ferritin and H-chain variant depleted of the ferroxidase site, however, showed markedly reduced uptake kinetics and comprised cores of increased diameter and regularity. Depletion of the inner surface Glu residues, whilst maintaining the ferroxidase site, resulted in a partially reduced rate of Fe uptake and iron cores of wider particle size distribution. Modification of both ferroxidase and inner surface Glu residues resulted in complete inhibition of iron uptake and deposition. No cores were observed by electron microscopy although negative staining showed that the protein shell was intact. The general requirement of an appropriate spatial charge density across the cavity surface rather than specific amino acid residues could explain how, in spite of an almost complete lack of identity between the amino acid sequences of bacterioferritin and mammalian ferritins, ferrihydrite is deposited within the cavity of both proteins under similar reconstitution conditions.